kmk: *** No rule to make target `G:/VirtualBox-4.3.10/out/win.amd64/release/lib/VBox-libcurl-x86.lib', needed by `G:/VirtualBox-4.3.10/out/win.amd64/release/obj/VBoxRT-x86/VBoxRT-x86.dll'. Stop.

Indeed, I can't seem to find any rule to make VBox-libcurl-x86.lib in the Makefiles, so I think something is missing. I tried copying the libcurl static libs to this name, but I get a lot of unresolved symbols.

Rename libcurl.lib to VBox-libcurl-x86.lib and copy it to out/win.amd64/release/lib/do the same thing to openssl libs (libcrypto and libssl), I used x86 libs for these cases.

Also, I needed to copy mingw64 nm.exe to (L:)\bin, where L is wherever the ose is. There were some issues with SDK path also, some makefiles don't like paths with spaces, so installing SDK to some path without space in the name may help.